1. Field of the Invention
The present invention relates to a seat back frame for use in an automotive seat, which allows an armrest to be mounted to one lateral side thereof. Particularly, the invention is directed to the seat back frame of the type wherein a large size of armrest can be mounted to one lateral side thereof.
2. Description of Prior Art
Recently, some of automotive seats are equipped with a large size of armrest at one lateral side of a seat back thereof. In most cases, such large size of armrest is rotatably mounted to the lateral side of seat back to allow for providing a wide support area on which an arm of a seat occupant can be comfortably rested.
However, since the large size of armrest is naturally increased in weight, an unexpected excessive load is applied therefrom intensively to one side of the seat back, with it being therefore of a high likelihood that a seat back frame in the seat back will be twisted and damaged due to such excessive load.
To solve such problem, generally stated, it is necessary to reinforce the seat back frame itself to a satisfied degree by increasing a thickness of each constituent part thereof, such as a side frame member to which the large-sized armrest is directly mounted and other peripheral frame members connected with the side frame member.
As a consequence thereof, such intricately reinforced seat back frame is found defective in not only increasing costs and number of required parts, but also encountering the difficulty to reform it directly into an ordinary seat back frame without any armrest mounted thereto. Thus, conventionally, the seat back frame itself can not be directly used in the case where the large-sized armrest is mounted thereto, as a result of which, it is required to provide two separate forming dies, including two separate press dies, one of which is designed for forming an ordinary seat back frame without requiring armrest, and another of which is designed for forming a seat back frame of robust structure sufficient to allow a large-sized armrest to be mounted thereto, which further undesirably increases costs involved.